Production of relatively straight chain alkyl aromatic hydrocarbons



Patented Aug. 16,1949

PRODUCTION OF CHAIN ALKYL BONS RELATIVELY s'rnucn'r AROMATIC monocu-Warren W. Johnstone, Riverside-Alt, asslgnor to Universal Oil ProductsCompany, Chicago,

a corporation of Delaware No Drawing. Application November 29, 1946,Serial No. 713,071

6 Claims.

The present invention relates to a process for the production of aspecific type of alkyl aromatic hydrocarbon having a molecular structureand containing a particular type of alkyl substituent which renders saidaromatic alkylate especially useful for the production of detergentstherefrom, said detergents being characterized as the alkali metalsulfonate salts of the alkyl aromatic hydrocarbon produced by theprocess of this invention. More specifically, the invention concerns animprovement in said process for producing alkyl aromatic hydrocarbons,which comprises subjecting an olefinic charging stock of specificcomposition utilized in the preparation of said aromatic alkylate to aparticular pretreatment prior to the alkylation reaction in which thealkylate is formed.

The type of detergent, for the production of which the present alkylaromatic hydrocarbon product is utilized as starting material, mayberepresented by the following structural formula:

n Rr produced by a process involving the alkylation of a benzenoidaromatic hydrocarbon containing the radicals R and R." selected from thegroup consisting of hydrogen, methyl, and ethyl radicals with anolefinic hydrocarbon fraction containing olefins having from about 9 toabout 18 carbon atoms per molecule to form the alkylate represented asan alkyl aryl hydrocarbon containing the substituents R, R" and R, inwhich R represents the group introduced'by the alkylation reaction. Thealkylate product is thereafter separated into a fraction containing thedesired alkylate which upon sulfonation introduces the sulfonic acidradical on the aromatic nucleus. The resultant alkyl aryl sulfonic acidwhen neutralized with an alkali base, the metallic anion thereofreprcsentedby M in the above formula, forms the alkyl aromatic sulfonatesalt comprising the detergent product herein referred to. It is oneobject of the present invention to provide a process for the productionof an alkyl aromatic hydrocarbon containing no more than 2 I one alkylgroup of fromabout 9 to about 18 carbon atoms of a relativelynombranched chain structure and containing in addition no more than twoother alkyl groups of more than two carbon atoms per alkyl group.

Another object of this invention is to provide a 7 process for removingtertiary and other highly branched chain olefins as well as polyolefinsfrom a hydrocarbon fraction containing desirable monoolefins of fromabout Cato about C a chain length per molecule, and thereafteralkylating a benzenoid hydrocarbon with said treated olefinic fractionto form an alkylate product particularly useful as starting material forthe production of detergents by subsequent sulfonation andneutralization. Still another object of the invention is to removeundesirable components normally present in olefinic fractions of fromabout C9 to a C18 chain length utilized in alkylating an aromatichydrocarbon for the ultimate production of detergents.

One embodiment of the present invention relates to a process for theproduction of an alkyl aromatic hydrocarbon, the alkyl group of which isof relatively straight chain configuration containing from about 9 toabout. 18 carbon atoms which comprises in combination the steps ;oftreating an olefinic hydrocarbon fraction boiling from about 150 toabout 225 C. with sulfuric acid of from about to about concentration toremove from said fraction highly branched chain olefins and polyolefins,separating an acid phase from a hydrocarbon phase and alkylating anaromatic hydrocarbon with said hydrocarbon phase.

In a more specific embodiment of my invention, the present processcomprises treating an olefinic hydrocarbon fraction boiling from aboutto about 225 C. with sulfuric acid of from about 85 to about 100%concentration in an amount thereof within the range of from about 2 toabout 25 pounds of acid per barrel of olefinic hydrocarbon fraction,removing an acid phase from a hydrocarbon phase, and subsequentlyalkylating a benzenoid hydrocarbon with said hydrocarbon phase to forman alkyl aromatic hydrocarbon utilizable as charging stock for theroduction of detergents.

Other specific embodiments of the process comprising this inventionrelate to operating condiable in the alkylation stage, and to otherfactors affecting the production of the present alkyl aromaticproduct,.which factors will hereinafter be referred to in greaterdetail.

I have found in an attempt to improve the quality and effectiveness ofalkyl aromatic sulfonate detergents that the product is markedlyaffected by the character and particularly the molecular composition andstructure of the alkyl aromatic hydrocarbon portion of the product.Detergents of optimum quality, for example, are formed when one, but nomore than one, of said alkyl substituents is a hydrocarbon radical ofrelatively straight chain configuration corresponding in chain length toat least a nonyl radical but of no greater chain length than anoctadecyl radical. It is further shown that detergents of the aboveindicated type progressively decrease in quality as the number of alkylsubstituents attached to the benzenoid nucleus, other than said longchain alkyl group, is increased beyond two Realizing the optimumproperties and constitution desired of the above alkyl aromaticsulfonate type of detergents, various attempts at commercial productionof the alkyl aromatic hydrocarbon portion of these detergents have beenundertaken. Heretofore, however, the production of the above desiredtype of detergent alkylates has often eecaanpanied by high operating andmaterial costs occasioned by the unavoidable, simultaneous production ofa large proportion of alkyl aromatic hydrocarbons containing shorterchain alkyl groups than the product desired. The formation of the latterundesirable alkylates necessarily involves the corresponding consumptionof the relatively costly aromatic reactant and when the product containsa large proportion of alkyl aromatic hydrocarbons unsuitable forconversion into detergents, material costs become excessive. Theformation of the latter alkylates undesirable for the production ofdetergents therefrom, is occasioned by the fact that certain componentsnormally present in the CaC1s olefinic hydrocarbon alkylating fractiondepolymerize into shorter chain olefins under the alkylating conditionsusually employed. The latter short chain olefins alkylate the aromatichydrocarbon as readily and .in some cases more rapidly than the desiredlong chain olefins, thereby producing alkylates containing one or moreshort chain alkyl groups which when sulfonated and neutralized do notyield the preferred and more efllcient type of detergent describedabove. In an investigation of the factors influencing the formation ofalkylates containing short chain alkyl groups, I have found that thehighly branched chain olefinic components of the alkylating charge andespecially the olefins containing tertiary carbon atoms are particularlysubject to cracking reactions in the presence of an alkylation catalyst.It is also true that where polyolefinic components (especiallydiolefins) are present in the alkylating charge, these hydrocarbonsenter the catalyst phase, polymerize, and effectively dilute thealkylation catalyst as well as reducing its activity by removing aportion of the catalyst in the form of a catalyst-hydrocarbon complex.Furthermore, even when the undesirable branched 4 chain olefins do notcrack during the alkylation reaction, the alkylates formed thereby donot contain the preferred straight chain alkyl groups. By means of thepresent invention whereby the oleflnic alkylating charge is pretreatedprior to the alkylationreaction with sulfuric acid to remove not onlythe highly branched chain olefins but polyoleilns as well, it has beenfound that the undesired components are selectively removed from thealkylating charge and the alkylates formed in the alkylation reactionare of the preferred type which yield superior detergents.

It is the principal feature of this invention, therefore, to provide aprocess for selectively removing the undesired. olefins from thealkylating charge.

Olefins containing from about 9 to about 18 carbon atoms per moleculewhich are utilizable in the process herein described may be obtainedfrom any suitable source. Such olefins are most .conveniently derivedfrom the olefinic fractions of thermally cracked petroleum productsboiling from about to about 300 C. and preferably those boiling in therange of from about 180 to about 225 C. (commonly referred to as apressure distillate fraction). Another source of olefins utilizable ascharging stocks herein, which in some cases is the preferred olefiniccharging stock, are the polymers produced by the catalytic or thermalpolymerization of short chain olefins, preferably those containing from2 to 4 carbon atoms per molecule. Both of the above common sources oflong chain olefins utilizable as alkylating charge herein, besidescontaining the desired olefins of straight chain structure, also containolefins having one or more secondary or tertiary carbon atoms and otherolefins having more than one double bond per molecule which readilycrack or depolymerize at relatively mild temperature conditions,especially when such olefins are subsequently contacted with analkylation catalyst at conditions normally tending to catalyze thecracking of said olefins as a side reaction of the principal alkylationreaction. As a result of these side reactions or the production of thecracked short chain olefinic hydrocarbons, the formation of undesiredalkylate is increased causing a simultaneous increase in the consumptionof the aromatic hydrocarbon starting material and, further, an increasein the amount of alkylation catalyst converted to spent catalyst sludgeby virtue of the formation of an olefinic hydrocarbon-catalyst additioncomplex comprising the sludge. The formation of the catalytically inactive sludge necessitates frequent addition of fresh catalyst to thealkylation reactor and/or frequent regeneration of the catalyst toremove the contaminating hydrocarbons contained in the sludge. It thusbecomes desirable to remove those highly branched chain olefins andpolyolefins contained in the alkylating charging stock not only from thestandpoint of effecting an economy in the consumption of the aromaticreactant and of the alkylation catalyst, but also for the purpose ofproducing a more selective alkylate from which superior detergents canbe prepared.

According to the operation of the present invention, the olefinichydrocarbon fraction utilized as the alkylating charge, whether obtainedfrom the polymerization product of short chain olefins or separated asan olefinic fraction Of a cracked petroleum distillate is treated withsulfuric acid to selectively remove therefrom the hereinabove namedundesirable components of the alkylating charge.

The method of treatment herein provided consists in intimatelycontacting the olefinic alkylating charge with sulfuric acid of fromabout 85 to about 100% concentration ata temperature sufficient to reactwith the secondary, tertiary, and polyolefinic components only, leavingsubstantially unaffected the desired straight chain mono-olefins. It isusually sufficient to efiect the operation at temperatures below about100 C. and preferably at temperatures below about 40 C., and above about20 C. although the temperature factor is also mutually dependent uponother conditions, such as the concentration of acid, the period ofcontact between the alkylating charge and acid. and the degree of mixingthe hydrocarbon and sulfuric acid phases. Although it is generallynecessary to utilize from about 2 to about 25 pounds of acid of theabove concentration per barrel of olefinic alkylating harge treated(each barrel representing 42 U. S. gallons), the latter factor is mostadvantageously determined by the gradual addition of the acid reactantto a given quantity of the hydrocarbon fraction and continuing theaddition of the acid until the maleic anhydride value determined on theeffluent treated product has been reduced to a low predetermined valueindicating substantially complete removal of diolefins from theefiluent. In a process of the present nature, the total effect of whichis dependent upon several variables, it is necessary to correlate thevarious operating conditions to correspond to the particular chargingstock utilized and said correlation is best determined by trial. Thetreatment is generally completed after a period of contact which mayrange from several seconds to 2 or more hours depending upon theconcentration of treating acid, the amount of undesirable olefins in thecharge, etc. The mixture is preferably stirred vigorously during thetreatment to effect intimate contact of the reactants. Following thespecified treating period, an acidic phase is separated from theremaining olefinic hydrocarbon phase and, if desired, the hydrocarbonphase may be given several water washing treatments and dried to preparethe hydrocarbons for the alkylation stage of the present process.

A convenient and readily available source of acid for treating theolefinic charge is the spent sulfuric acid recovered from other treatingor conversion processes in which sulfuric acid is employed as reagent orcatalyst. Thus, the sulfuric acid phase of an alkylation reaction inwhich the acid is utilized .as catalyst may be used as the treating acidin the present process. This source of acid is especially applicablewhere the concentrated acid is used for alkylating the aromatic reactantin the production of detergent alkylates.

It is to be emphasized that although the process is particularlyapplicable to the production of alkyl aromatic hydrocarbons fordetergent manufacture, the process may also be employed for theproduction of any alkyl aromatic hydrocarbons utilizing the chargingstocks herein specified and from which process it is ultimately desiredto manufacture a product containing predominantly long chain alkylaromatic hydrocarbons free of polyalkylates containing a multiplicity ofshort chain alkyl groups.

Of the aromatic hydrocarbons utilizable herein for the production of thepresent alkyl aromatic hydrocarbon product by alkylation thereof withthe aforementioned olefinic hydrocarbon fraction, I prefer to utilize abenzenoid aromatic hydrocarbon containing no more than 2 alkylsubstituents, especially when said product is to be utilized for theproduction of detergents by subsequent sulfonation thereof. Preferably,neither of said alkyl substituents are of greater chain length than theethyl radical and more desirable still are methyl radicals. Thus,benzene, toluene, xylene, methylethyl benzene and diethyl benzenecomprise aromatic hydrocarbons of the above preferred type and of thisgroup it is preferred to utilize benzene and toluene for the productionof detergents having the highest degree of detersive action. When alkylaromatic hydrocarbons are desired for purposes other than detergentproduction, it is also within the scope of the present invention toutilize other benzenoid as Well as polycyclic aromatic hydrocarbons asthe reactant to be alkylated. Thus, any alkylatable aromatic hydrocarboncontaining a nuclearly substitutable hydrogen atom may be utilized inthe alkylation reaction, including such compounds as the triandtetra-aikyl benzenoid hydrocarbons, as for example, mesitylene, 1,2,3-trimethyl benzene, etc. or the polycyclic aromatic hydrocarbons such asnaphthalene, etc. and its alkylatable alkyl derivatives.

In the alkylation stage of the present process, the aromatic reactantand treated olefinic alkylating charge may be introduced simultaneouslyor in admixture with each other into the alkylation reactor containingthe desired alkylation catalyst or alternatively the aromatichydrocarbon may be contacted with the alkylation catalyst followed bythe addition of the olefinic alkylating charge thereto. The molecularproportion of aromatic hydrocarbon and treated olefinic fractionintroduced into the alkylation reactor is generally maintained above anequimolecular ratio, preferably from about 2 to 1 to about 30 to 1 oreven higher to minimize polyalkylation of the aromatic reactant. Anysuitable alkylation catalyst may be utilized to effect the condensationof the olefinic and aromatic hydrocarbons among which may be mentioned:(1) sulfuric acid of from about to about 100% or higher concentration,said higher concentration containing free sulfur trioxide up to about15% of the latter component, (2) substantially anhydrous hydrogenfluoride, generally not containing more than about 10% water, (3)anhydrous aluminum chloride or aluminum bromide, preferably in thepresence of the corresponding hydrogen halide, (4) boron trifiuoride,with or without addition thereto of hydrogen fluoride, (5) a sulfonicacid of either alkane or aromatic derivation, (6) a phosphoric acid,preferably pyrophosphoric acid, which is desirably deposited on aseparating or spacing material such as alumina or a siliceous materialsuch as hydrated silica, kieselguhr, kaolin, etc. and (7) hydrogenchloride, usually in the anhydrous condition. The preferred alkylationcatalyst of my invention comprises hydrogen fluoride of from about toabout concentration or sulfuric acid of about 95% concentration, theorder of preference being in the order named.

When utilizing the above specified ratio of aromatic reactant toalkylating olefinic hydrocarbons, said hydrocarbons are maintained inthe alkylation reactor in contact with the alkylation catalyst for areaction period which may vary from about 5 to about 80 minutes, theparticular time of-reaction depending upon the relative case ofalkylating the selected charge stocks. The temperature maintained in thealkylation reactor in the presence of the above preferred alkylatingcatalyst is within the range of from about 30 to about 100 C.(preferably from about to about 50 0.). Superatmospheric pressures,sufficient to maintain the catalyst and hydrocarbons in liquid phase arepreferably maintained during the alkylation reaction, although pressuresin excess of 100 atmospheres are usually not required. The processconditions vary with the particular charging stock and with theparticular catalyst utilized to effect alkylation, but the conditionsnecessary to fix these variables are well known to those skilled in theart of alkylating hydrocarbons so that they may be readily determinedwhen the above variables are known.

Following the alkylation reaction, the products formed thereby may beseparated by fractionating the desired alkyl aromatic hydrocarbonproduct from other hydrocarbons introduced into the alkylation zone. Theexcess aromatic reactant, usually the lowest boiling fraction, may beseparated and recycled to the alkylation reactor. Although the presentprocess is characterized by the production of minimum amounts of shortchain alkyl aromatic hydrocarbons, a small amount of these willordinarily be formed in spite of the precautions taken to avoid their.formation and these are separable from the product of the alkylationreaction as an intermediate fraction. The desired alkyl aromaticproduct, boiling from about 260 to about 345 C. when toluene is thearomatic selected for alkylation, is separated as a bottoms fractionupon fractionally distillating the total alkylation product atvatmospheric pressure. In order to separate a purified product boilingwithin a particular temperature range, the bottoms fraction isordinarily subjected to vacuum distillation and the desired fractionseparated from the distillate. The following examples are introduced forthe purpose of further illustrating the process herein described forproducing alkyl aromatic hydrocarbons containing a single long chainalkyl group of relatively non-branched structure containing from about 9to about 18 carbon atoms per group. The conditions specified thereinhowever, should not be construed as limiting the generally broad scopeof this invention in strict accordance thereto.

A pressure distillate fraction boiling from about 170 to about 220 C.containing olefins of from about C9 to about C15 chain length recoveredfrom the thermally cracked products of a Trinidad gas oil fraction wasutilized in the following examples to alkylate toluene for the ultimateproduction of detergents from the toluene alkylate. The fraction hereinutilized, typical of pressure distillate fractions, containedapproximately'28% by weight of unsaturates, predominantly of olefiniccharacter. In Example I below, the pressure distillate alkylating chargewas utilized as received, Without pretreatment with the sulfuric acidextractant herein provided prior to the alkylation reaction, while inExample II, the pressure distillate alkylating charge derivedfrom thesame source was subjected to an acid treatment with sulfuric acid priorto the alkylation stage; yields are included in each example to indicateconclusively the advantage of acid pretreatment. r

EXAMPLE I 7.5 pounds (3.5 liters) of hydrogen fluoride was added to aturboreactor and cooled to about 4 C. at a pressure of about 100 poundsper square inch gage. 2680 cc. (25.2 mols) of toluene were pumped intothe reactor followed by 1 liter (1.5 mols) of the above indicatedpressure distillate fraction. The latter fraction was introduced intothe mixture of hydrogen fluoride and toluene over a period of 30 minutesas the mixture was Table I Yield, lbs. 1 315 Identity g g agg range' nocharged 50-125 Toluene (Recovered) 2, 016 125-190 Olefins plus aromaticsll. 1

190475 Olefins plus short chain 289 alkyl aromatics.

275-325 lkyl e 288 275-345 .--do 1 450 1 Total alkylate utillzable indetergent manufacture.

EXAMPLE II A portion of the same pressure distillate fraction utilizedin Example I as the alkylating charge, was given an acid pretreatment bymeans of the following procedure: 1708 cc. of the indicated pressuredistillate fraction was rapidly stirred with 25.5 cc. of sulfuric acid(corresponding to 10 pounds of acid per barrel of pressure distillate)added thereto at 25 C. The two phases were stirred for an additional 10minutes and then allowed to settle into separate layers, the acid layerbeing drawn off from the hy drocarbon layer and hydrolyzed by theaddition thereto of an equal volume of water. Hydrolysis caused theseparation of 30 cc. of a viscous oil having properties different fromthe pressure distillate from which it was separated. The volume,

of the hydrocarbon phase separated in the settler from the acid was 1645cc., representing a loss of 63 cc. of the pressure distillate to thesulfuric acid extractant. The recovered, treated olefins were utilizedas alkylating charge in the following alkylation reaction.

8.34 pounds (3.78 liters) of hydrogen fluoride was added to aturboreacto'r and cooled to about 2 C. at a pressure of pounds persquare inch gage. 2343 cc. of toluene (22.2 mols) was pumped into thereactor followed by the addition of 1068 cc. (1.6 mols of olefins)thereto of the acid treated pressure distillate fraction prepared asindicated above. The latter pressure distillate was introduced into'thestirred mixture of toluene and hydrogen fluoride over a period of 23minutes, the temperature being maintained at about 2 C. Stirring wascontinued for 5.7 hours and the mixture was then allowed to settle, anupper hydrocarbon layer separating from a lower acid layer on standing.The hydrocarbon layer was defiuorinated and fractionally distilled, thefollowing Table II indicating the yields and properties of thehydrocarbons recovered.

1 Where the pounds of olelin charged is calculated on the basis of thepressure distillate containing approximately 28% olefins.

' otal alkylate utilizable in detergent manufacture.

A comparison of the results of Example I and Example II indicate that anincrease in the alkylate yield utilizable from 0.53 pound of alkylateper pound of olefin charge to 0.77 is'obtained when utilizing an acidtreated pressure distillate from which undesirable olefins andpolyoleflns are removed as the alkylating charge.

I claim as my invention:

1. A process for the production of an alkyl aromatic hydrocarbon, thealkyl group of which contains from about 9 to about 18 carbon atoms ofrelatively straight chain configuration which comprises in combinationthe steps: treating an olefinic hydrocarbon fraction boiling from about150 to about 225 C. with sulfuric acid of from about 85 to about 100%concentration to remove therefrom highly branched chain olefins andpolyolefins, separating acid from hydrocarbons and alkylating anaromatic hydrocarbon with the sulfuric acid treated olefinic hydrocarbonfraction.

2. A process for producing an alkylated benzenoid hydrocarbon having thestructural formula wherein R is a relatively straight chain alkyl fordetergentproduction of radical containing from about 9 to about 18carbon atoms and R and R" are selected from the group consisting ofhydrogen, methyl and ethyl radicals, said process comprising incomblnatlon the steps: treating an olefinic hydrocarbon fraction boilingfrom about 150 to about 225 C. with sulfuric acid of from about to aboutconcentration to remove therefrom 10 highly branched chain oleflns andpolyolefins. separating an acid phase from a hydrocarbon phase andcontacting said acid treated olefinic fraction at alkylating conditionswith a benzenoid hydrocarbon corresponding in structure to wherein R andR" are as indicated for said above alkylated benzenoid hydrocarbon.

3. The process of claim 1 further characterized in that the olefinicalkylating charge is contacted with the sulfuric acid treating agent ata temperature below about 100 C.

4. The process of claim 1 further characterized in that the olefinicalkylating charge is contacted with the sulfuric acid treating agent ata temperature below about 40 C. and above about -20 C.

5. The process of claim 1 further characterized in that the olefinicalkylating charge is contacted with from about 2 to about 25 pounds ofsaid sulfuric acid per barrel of olefinic alkylating charge.

6. The process which comprises treating an olefinic alkylating chargecontaining olefins having from about 9 to about 18 carbon atoms permolecule with sulfuric acid of from about 85 to about 100% concentrationat a temperature below about 100 C., separating a predominantly acidphase from the olefinic hydrocarbon phase, contacting said hydrocarbonphase with a benzenoid hydrocarbon at alkylating conditions in thepresence of an alkylation catalyst, separating from the resultingreaction products an alkylate fraction containing an alkyl aromatichydrocarbon having a relatively straight chain alkyl group of from about9 to about 18 carbon atoms per group utillzable in the production ofdetergents.

- WARREN W. JOHNSTONE.

REFERENCES orrEn The following references are of record in the flle ofthis patent: I

UNITED STATES PATENTS Number Name Date 2,007,160 Engs et al. July 9,1935 2,232,117 Kyrides Feb. 18, 1941

